1. The Field Of The Invention
The present invention relates to a device for cross connecting a plurality of key telephone sets within a specific location to several incoming lines and, in particular, to a cross connecting device which allows unskilled personnel to effect correct interconnection of an internal telephone system.
2. The Prior Art
The installation of a customer telephone system on a particular premises, and in particular to the rearrangement of the telephone system as the customer's business expands and/or the arrangement of personnel is revised and relocated, is a major factor in both the installation and maintenance costs of such a system. It is estimated that the current costs of switching telephone lines connected to a key set telephone may be as high as 60 to 70 dollars. Most of this expense is in labor costs.
The present practice is to have entrance cables or lines from a central telephone office terminate at a terminal room in an office building or the like. The terminal room is normally adjacent to an equipment room which primarily houses PBX equipment, and the like, which is required for the particular customer needs. Generally there are also a number of apparatus or satellite rooms located throughout the building and which contain equipment regarding service to particular defined areas within the building, for example a floor, a wing, a particular office or an office complex. As a specific example, a single floor of a modern office building might contain several suites of offices relating to a number of separate businesses, such as professional offices of doctors, lawyers, engineers, etc., or a number of commercial enterprises, such as sales office for a number of separate corporations. Each of these suites of offices would have their own internal telephone system, which currently requires the services of a skilled technician for installation since each key telephone is connected to the incoming lines by a cable, usually made of twenty-five individual wire pairs, each of which must be terminated according to a defined pattern on a contact board, such as the one described in U.S. Pat. No. 3,777,223. If the cross connections allowing the various telephone key sets to respond to various designated incoming lines are to be changed, then the wires of the cables, which were inserted into the associated contact board by the craftsman, must be removed from their contact slots and rearranged according to the new desired configuration. The common 25 pair cable would require at least three pairs of conductors from the Red field to be reconnected to the Blue field. An extra pair would also have to be reconnected to have ring at the key set and it may be necessary to add a diode matrix block to the system and run several pair more of "split common audible" conductors. It becomes readily apparent that there will be many instances when the wires being rerouted will be too short and therefore require either pulling a new cable through the appropriate conduits or splicing additional lengths of wire to the existing cable wire. Of course these additional wire lengths must conform to the color code when attached to the cable. Further, the connections must be in a specific sequence since any missed count or reversed pair may damage the equipment or render the entire system inoperative. Also, the abovementioned diode matrix blocks are rarely used since they are easily installed wrong.
Most telephone key sets come in standard six and 10 button models capable of handling five and nine incoming lines respectively. The remaining button is reserved for "hold". The cross connection of these key sets with incoming lines to the office and, in particular, the temporary cross connection of certain telephone key sets to handle calls from other lines, as may be required by personnel absenses due to business, vacation, and the like, is an expensive and time consuming problem since this work can only be correctly accomplished by the highest skilled craftsmen of the telephone company. The current labor costs involved are usually too high to justify going to such an expense for only a temporary period, especially since much of the expense is for work which is erased when the system is returned to the original condition. Also the time delays in getting this work done can obviate the requirement for the temporary change.
U.S. Pat. No. 3,869,582 discloses a general scheme for interconnecting telephone incoming lines and specific locations. However, the described scheme raises a number of unanswered questions when applied to key set type telephones. For example, FIG. 6 shows a standard circuit concentration bay termination manufactured by Amphenol, as mentioned in column 3, line 13. This is a non-polarized connector and raises the strong possibility of having reversed leads between ring and tip connections. Such reversals will definitely create a no operation condition of push-button key set telephones and may cause failures in some types of equipment. Thus they definitely would not be suitable for use by untrained personnel. The four contact panels, as well as the four contact plugs and receptacles, (as shown in FIGS. 7A, 7B, 8A, and 8B of the drawings) are inadequate for use with "key set-type telephones" since most key set telephones currently in use utilize one or more twenty-five pair cable connectors, such as the one described under U.S. Pat. No. 3,777,223. Also, use of unpolarized connectors for jumpering purposes with key set telephones would create chaos with the KTU (Key Telephone Unit) line cards, as well as the KSU (Key Service Unit) in the equipment room, which would result in equipment failure. Again, trained personnel would be required to change connections. The use of any connectorized system for changing lines without a diode matrix would be difficult (see Bell System Practices AT&T Co., Standard, Section 461-620-100, Issue 2, Dec. 1971, Matrix Block 1A1 System). Normally, each line on each key set telephone is connected to a separate bell, i.e., six lines, six bells or a diode matrix block. Otherwise there would be feedback and unactivated lines would have their bells ringing regardless of which line had the incoming call. Either of these methods would require the more highly skilled telephone craftsman to install or change.